// make JSON response writers available by default
if (responseWriters.get("json")==null) {
responseWriters.put("json", new JSONResponseWriter());
}
if (responseWriters.get("python")==null) {
responseWriters.put("python", new PythonResponseWriter());
}
if (responseWriters.get("ruby")==null) {
responseWriters.put("ruby", new RubyResponseWriter());
}